As an image display apparatus capable of large screen display, a projection type projector apparatus is known. A viewer can view a projected image by projecting light from a light source onto a screen.
As a light source of a projector apparatus, a high luminance projection tube has been used until now. However, with the object of the improvement of brightness, color reproducibility and the like, the object of the easiness of modulation by an image signal, and the other objects, a projection system using the laser light sources of red (R), green (G) and blue (B) has been proposed.
In the mean time, when a laser light is used, the securement of the safety thereof is an important task. For example, it is needed to take an enough measure against the case where a viewer carelessly enters the projection area of the laser light. That is, a danger in the case where a laser light directly entered the eye is pointed out. As the safety measure thereof, various apparatus having the function of detecting entry into the projection area of the laser light by a person or the like to cut off the projection of the laser light has been proposed (for example, see Japanese Unexamined Patent Publication No. Hei 4-111585, Published Japanese Translation of PCT Application No. Hei 11-501419, Japanese Unexamined Patent Publication No. 2001-249399).
Now, the conventional apparatus have the problems caused by taking such a safety measure. The problems are, for example, that the configuration of an apparatus becomes complicated; that such a measure interferes with making the size of an apparatus larger; and the like.
That is, a safety mechanism for the safety of the human body is indispensable for an apparatus attaching importance to the safety. However, when the attachment of the safety mechanism brings about disadvantages such as the growth of the complexity of a projection optical system and the like, a remarkable rise of an apparatus cost, and the like, it is apprehended that the disadvantages cause a hindrance of diffusion and the like. Moreover, no delay of the operation of the safety mechanism is allowed, and the rapidity of entry detection is required.
Accordingly, the present invention aims to improve the safety of an image projection apparatus including the function of projecting an image on a screen to display the image thereon in the case where the human body or the like enters the projection region of a radiation light, and not to bring about the increase of the complexity of the configuration of the apparatus, and the like owing to the improvement of the safety.